Valone 1981.

Study characteristics
Methods	Study design: retrospective cohort longitudinal Location: USA Time period: 1980 Outcome: PDR Outcome measurement: incidence
Participants	Number of participants: 203 Diabetes type: not reported Inclusion criteria: PDR in one eye, NPDR in fellow eye  Exclusion criteria: no prior treatment of DR; no other retinal disease at baseline
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/pbuwn/?view_only=33735ad697a14fa787b4f047918ffa56
Item	Authors' judgement	Support for judgement
Study participation	Unclear	See ‘Notes’ above for link to risk of bias assessment
Study attrition	Unclear	See ‘Notes’ above for link to risk of bias assessment
Prognostic factor measurement	Unclear	See ‘Notes’ above for link to risk of bias assessment
Outcome measurement	Unclear	See ‘Notes’ above for link to risk of bias assessment
Adjustment for other prognostic factors	No	See ‘Notes’ above for link to risk of bias assessment
Statistical analysis and reporting	Unclear	See ‘Notes’ above for link to risk of bias assessment